946 Controller Instruction Manual
pg. 117
11.2.2 Clean the I-Mag Sensor
Depending on the degree of contamination and the application of the sensor, the internal parts may be
cleaned — either ultrasonically, with mild abrasives, or chemically.
Do not touch any vacuum-exposed part after cleaning unless wearing gloves.
Ultrasonically clean surfaces using only high quality detergents compatible with aluminum (i.e.
ALCONOX®).
Scrub with a mild abrasive to remove most contamination. Scotch-Brite™ or fine emery cloth may be
effective. Rinse with alcohol.
Clean aluminum and ceramic parts chemically in a wash (not recommended for semiconductor
processing), such as a 5 to 20% sodium hydroxide solution, at room temperature (20°C) for one minute.
Follow with a preliminary rinse of deionized water. Remove the black residue left on aluminum parts in a
50 to 70% nitric acid dip for about 5 minutes.
Chemical cleaning should not be used to clean the anode; mild abrasives or
ultrasonic cleaning are acceptable.
Do not damage the leaf spring
1
while cleaning or assembling the sensor.
Each of the cleaning methods described above should be followed with multiple rinses of deionized water.
Dry all internal components and the sensor body
9
in a clean oven set at 150°C. The two ceramic
spacers,
4
and
7
, are slightly porous and will require longer drying time in the oven to drive off the
absorbed water.
11.2.3 Assemble the I-Mag Sensor
Wear gloves and assemble with clean tools.
1. Roll the sensor body
9
on a flat surface and, looking down the port, check the anode
10
for
any radial runout motion. It should be straight and centered with the sensor body
9
for proper
operation.
2. Install the ground shield
8
using tweezers. Make sure that the
ground shield
8
drops into the locating collar
11
.
3. Slide the small ceramic spacer
7
over the small end of the ground
shield
8
.
4. Check that the leaf spring
1
will contact the base of the cathode
6
, as shown to the right. If not, remove the small ceramic spacer
7
and the ground shield
8
, and gently bend the leaf spring
1
towards the anode
10
and then replace the ground shield
8
and
ceramic spacer
7
.